Alcohol and GABAergic Transmission in the Developing Neocortex

描述（由申请人提供）：胎儿酒精综合征（FAS）仍然是导致出生缺陷的主要原因之一。虽然可以通过在怀孕期间戒酒来预防，但在美国，FAS的估计发病率为每1000例活产0.2至1.0例。目前尚无可预防的FAS治疗方法。发育期间乙醇暴露影响中枢神经系统，从细微的结构和功能改变到广泛的神经元死亡。在乙醇（EtOH）暴露后，它如何引起广泛的神经元变性的机制尚未得到很好的表征。据推测，etoh诱导的细胞死亡是由于发育中的新皮层中神经元活性过度抑制所致。EtOH被认为与苯二氮卓类药物类似，通过增强突触后的GABAARs。然而，我们实验室之前的研究表明，EtOH通过增加GABA的释放来增加神经元的兴奋性。我假设EtOH增加GABA的释放，导致皮质层（第二层和第四层）的神经元兴奋，这些神经元因EtOH暴露而发生凋亡细胞死亡（第二层和第四层），而非皮质层（即第三层）。在具体目标#1中，我将结合使用全细胞和穿孔补丁电生理技术来确定EtOH是否对新生儿体感觉皮层INV层的gaba能传输有不同的影响。在具体目标#2中，我将通过结合使用松散细胞附着电生理和Ca2+成像技术来确定GABAAR的激活是否会导致相同神经元层的兴奋。如果我确定目标细胞的兴奋性增加，那么我将确定EtOH是否通过增加动作电位依赖性GABA释放来增加兴奋性。从长远来看，这些研究可能为针对未成熟神经元中GABAARs的兴奋作用的FAS的新型治疗干预的发展奠定基础。

DESCRIPTION (provided by applicant): Fetal alcohol syndrome (FAS) continues to be one of the leading causes of birth defects. Although it is preventable by abstaining from alcohol consumption while pregnant, the estimated incidence for FAS in the United States is 0.2 to 1.0 per 1000 live births. Currently there are no preventable treatments for FAS. It is well characterized that ethanol exposure during development affects the central nervous system ranging from subtle structural and functional alterations to widespread neuronal death. Following ethanol (EtOH) exposure, the mechanism as to how it causes widespread neuronal degeneration is not well characterized. It has been postulated that EtOH-induced cell death results from excessive inhibition of neuronal activity in the developing neocortex. EtOH has been thought to act like a benzodiazepine by enhancing GABAARs postsynaptically. However, previous work from our laboratory suggests that EtOH increases neuronal excitability, by increasing GABA release. I hypothesize that EtOH increases GABA release leading to excitation of neurons in cortical layers that undergo apoptotic cell death in response to EtOH exposure (layers II and IV) but not in layers that do not (i.e. layer III). In specific aim #1, I will use a combination of whole-cell and perforated patch-electrophysiological techniques to determine if EtOH is differentially affecting GABAergic transmission in layers INV of the neonatal somatosensory cortex. In specific aim #2, I will determine if activation of the GABAAR results in excitation in the same neuronal layers by using a combination of loose cell-attached electrophysiological and Ca2+ imaging techniques. If I determine that there is an increase in excitability of the target cell, I will then determine if EtOH increases excitability by increasing action potential-dependent GABA release. In the long-term, these studies might form the basis for the development of novel therapeutic interventions against FAS that target the excitatory actions of GABAARs in immature neurons. Lay summary: Fetal alcohol exposure is a common cause of mental disabilities in the U.S. The mechanism by which alcohol damages the developing brain are poorly characterized. The studies proposed here will increase our understanding of how alcohol affects the actions of the neurotransmitter GABA and in the long term might form the basis for the developmental treatments against this problem.